Recovering sulfonates of oilsoluble sulfonic acids from acid-treated hydrocarbon oils



Patented Aug. 22, 1950 RECOVERING SULFONATES OF OIL- SOLUBLE SULFONICACIDS FROM ACID-TREATED HYDROCARBON OILS George Riethof, Pittsburgh,Charles W. Montgomery, Oakmont, and George P. Brown, Jr., Pittsburgh,Pa., assignors to Gull. Research & Development Company, Pittsburgh, Pa.,a corporation of Delaware No Drawing. Application September 8, 1948,Serial No. 48,328

7 Claims. (Cl. 19641) This invention relates to an improved method ofrecovering sulfonates of oil-soluble sulfonic acids from acid-treatedhydrocarbon oils. More particularly, the invention pertains to animproved method of neutralizing a sulfonated oil by the use of analkylolamine, and separating the resulting alkylolamine sulfonic acidsalts from the neutralized oil.

In the sulfonation of viscous hydrocarbon oils, especially petroleumhydrocarbon oils of the lubricating oil range, an acid oil layer isproduced which contains dissolved sulfonic acids. This acid oil layer isseparated from the suliuric acid layer and is neutralized. In some casesit is neutralized with an alkylolamine such as ethanolamine. Theneutralization is carried out by adding the amine to the oil in smallincrements amid vigorous agitation until the oil shows a slightlyalkaline reaction. This produces a mix in which the sulfonates tend tobe emulsitied in the oil. The sulfonates are recovered by permitting theneutralized, slightly alkaline oil to settle over an extended period oftime, during which the bulk of the ethanolamine sulfonic acid saltsseparate out. To remove the rest, it has been found necessary to washthe sulfonates out of the oil with water or a solvent such as isopropylalcohol, etc.

Among the difiiculties experienced in practicing the prior art methodoutlined above is the frequent formation of relatively stable emulsionsor suspensions of amine sulfonic acid salts in the neutralized oil.Excessively long settling times are required before any appreciable partof the sulfonates settles out of the oil. The settled sulfonate layersare relatively much smaller in volume than the oil layers and sharpseparations of the oil and sulfonate layers are extremely diflicult, orimpossible to perform in conventional apparatus. Appreciable amounts ofthe sulfonates always remain suspended or mixed in with the oil layer,and it is necessary to recover them by the use of several water oralcohol washes employing large volumes of wash solvent. Additionaltroublesome emulsion problems are encountered in these subsequentwashing operations and long settling times, settling tanks or expensivecentrifuge equipment, are required to separate the solvent layer fromthe oil layer. Finall in actual practice the large volumes of washsolvents must be recovered from the sulfonates and the oil layer.

In view of the disadvantages of the prior art methods, it is an objectof the invention to pro- 2 vide an improved method for separatingsulfonic acids from acid oil.

It is a particular object of the invention to provide a rapid andconvenient method for the simultaneous production of oil-solublesulfonic acid salts and refined mineral oil.

Another object of the invention is to provide an economic method forrefining acid oil and recovering the refined oil substantially free ofimpurities without the use of large volumes of wash solvents.

We have discovered, in accordance with the invention, that alkylolaminesulfonic acid salts can be quickly and efiiciently prepared andseparated from the acid oil containing oil-soluble sulfonic acids byneutralizing the sulfonic acids with an alkylolamine incompletelymiscible with the neutralized oil and having 19. higher density thanthis oil, and using an excess of the alkylolamine. We have found thatthe excess alkylolamine is effective to dissolve the alkylolaminesulfonates and to separate from the oil an alkylolamine liquid layercontaining the salts after a very short settling time. The amount ofexcess alkylolamine, therefore, should be sumcient to dissolve thesulfonates, leaving at most a negligibly small quantity of thesulfonates in the oil and creating conditions producing a cleanseparation between the oil and alkylolamine layer. In the presentprocess the alkylolamine layer is separated from the oil layer and isthen treated for the recovery of the excess alkylolamine. We have foundthat the alkylolamine can be recovered efliciently by subjecting amixture containing salts of the sulfonic acids to vacuum distillationwhereby the alkylolamine is vaporized and recovered. The use of theexcess of the alkylolamine, therefore, does not present an economicproblem, since this excess is recovered and available for use insubsequent practice of the process. The sulfonates are recovered fromthe still bottoms.

In cases where the oil layer contains an im- I portant amount ofdissolved alkylolamine, this compound may be recovered by any suitablemethod. We prefer to use an alkylolamine having a boiling pointappreciably below the boiling range of the oil, preferably at least 20C. below the initial boiling point of the oil, and in this case the oillayer may be subjected to vacuum distillation to vaporize and recoverthe alkylolamine. The refined oil, substantially free of sulfonic acidsand the alkylolamine, is recovered from the still.

The process of the invention may be applied to sulfonated oils or acidoils obtained by the treatment of the original oils with a sulfonatingagent adapted to accomplish sulfonation of the oils. The usualsulfonating agents are concentrated or fuming sulfuric acid andchlorosulionic acid. The process is especially applicable to sulfonatedor acid oils obtained by sulfonation of lubricating oil stocks such asraw distillates and residuums: but acid oils resulting from treatment ofsolvent extracts of such lubricating oil fractions are preferred, sincethe refined oil obtained from the neutralized acid oil may be used tosupplement the supply of lubricating oil obtained as the railinate inthe solvent extraction. The extract oil may be produced by the use ofsuch solvents as furfural, aniline,

nitro-benzene, sulfur dioxide-benzene mixtures;

dichlorodiethylether, phenol, etc.

In accordance with a preferred manner of practicing the invention forthe treatment of an acid-treated lubricating oil, said lubricating Oilhaving an initial boiling point above 270 C., and using an alkylolamineboiling below the initial boiling point of the oil, preferably below250' C.. neutralization of the acid oil is performed by adding thealkylolamine to the oil in small increments while the oil is kept in astate of vigorous agitation, to achieve rapid and completeneutralization. Heat of neutralization is produced, which raises thetemperature of the agitated mixture, thus assisting the process ofneutralization. The addition of alkylolamine is continued until the acidoil is neutralized, as is evidenced by a slight alkaline reaction of themixture. If the addition of the alkylolamine is stopped at this stage,the resulting mixture has the appearance of an emulsion and is withdifficulty only partially separable into layers by settling. In thepresent process, the addition of alkylolamine is continued until anexcess of at least 5 per cent by volume based on the acid oil, ofalkylolamine, hasbeen added to the mixture. In some cases it may bedesirable to add considerably more than the amount mentioned above. Theresulting mixture is heated with occasional stirring at least to atemperature at which the emulsion breaks rapidly-about 80 C. in the caseof ethanolamine, and is then run into settling tanks and permitted tosettle. The settling is preferably accomplished at the elevatedtemperature of the mixture, which may be about 80 to 120 C. at thisstage. because more rapid stratification of the oil and alkylolaminelayers is accomplished at elevated temperatures; although the settlingmay be accomplished while the mixture is cooling to atmospherictemperature. In either case, a lower layer of alkylolamine, containingthe alkylolamine sulfonates in solution. settles out at the bottom ofthe settling tank in a relatively short period of time.

This lower layer is drawn off from the oil layer and the alkylolaminemay be recovered from the dissolved alkylolamine salts by eva oration.preferably by vacuum distillation. If it is desired to separate the sufonic ac ds as metal salts, the alkylolamine salts are decomposed inconventional manner by reacting them with the appropriate compounds suchas metal oxides, hydroxides or carbonates. The alkylolamine is thendistilled oil, preferably under vacuum.

The upper layer obtained in the above treatment contains the neutralizedoil in which is dissolved a small amount, which in many cases may beless than about 0.5 per cent, of alkyiolmine. The alkylolamine isrecovered from this layer by subjecting it to conventional distillationmethods at reduced pressure to vaporize the alkylolamine which is thencondensed in the conventional manner. In case the settling was completedat elevated temperatures, an additiox advantage is gained in that thehot oil layer be stripped free of the alkylolamine by simply reducingthe pressure above the oil layer in a suitable container. Thealkylolamine is flash-vaporized. The alkylolamine recovered from boththe salts and the oil is preferably reused in the process to reduceoperation costs. The oil stripped of alkylolamine is practicallycompletely free of salts and may be used directly as a lubricating oil,turbine oil, hydraulic oil, etc.

While it is usually preferred to recover the alkylolamine. dissolved inthe oil, the amine may be left in the 011 if desired, depending upon theamount of amine present and the intended application of the oil.

As previously stated, the alkylolamines suitable for use in the presentprocess are those incompletely miscible with the neutralized oil at thesettling temperature. The extent of the solubility of the alkylolaminein the oil is a critical factor inasmuch as the completeness ofseparation of the sulfonic acid salts from the oil layer is a functionof the relative amounts of alkylolamine remaining in the oil layer andin the alnlolamine layer below it. The lower the solubility of thealkylolamine in the neutralized oil, the more complete will be theseparation of the alkylolamine salts. In cases where an alkylolaminethat is relatively soluble in the neutralized oil is employed, effectiveseparation requires the use of an amount of the alkylolamineconsiderably greater than the amount necessary when using a less-solublealkylolamine. The aikylolamine should not be miscible in all proportionswith the neutralized oil at the settling temperature since in this caseno separation is possible. We prefer to employ an alkylolamine which issoluble in the neutralized oil in an amount less 5 than 5 per cent byvolume of the solution, and especially satisfactory results are obtainedwhen an alkylolamine which is soluble in an amount less than 2 per centby volume is used. In general, the amino group or groups should beunsubstituted, as the presence of such groups confers desired low oilsolubility to the alkylolamine.

In practice, the difference between the densities of the neutralized oiland alkylolamine should preferably be at least about 0.04 gram per cc.,with differences of at least about 0.09 gram Ethanolaminel-aminopropanol-2 3-aminopropanol-l 2-aminobutanol-l 4-aminobutanol-ll-aminobutanol-2 3-aminobutanol-2 l-amino-2-methylpropanol-2 's3-aminopentanol-2 2-aminopentanol-3 1-amino-2-methylbutanol-23-amino-2-methylbutanol-2 Z-aminohexanol-B 4-amino-2-methylpentanol-24-amino-2-methylpentanol-5 3-amino-2,3-dimethylbutanol-24-amino-2,4-dimethylpentanol-2 1-amino-2,5-dimethylhexanol-2 5-amino-2,5-dimethylhexanol-3 1,3-diamino-2-propanol The following examples aregiven for the purpose of illustrating the invention:

Example 1 To 200 parts by weight of acid oil, obtained from sulfonationwith 20 per cent by weight of concentrated sulfuricacid of an oilboiling in the lubricating oil range resulting from furfural extractionof a Texas lube oil distillate having a viscosity of about 400 S. U. S.at 100 F., and containing about per cent by weight of the solution ofoil-soluble sulfonic acids, is added with stirring, in increments, about5 per cent by weight of the acid oil, of technical monoethanolamine.This amount of monoethanolamine is several times that sumcient toneutralize the sulfonic acids. At this time the mixture gives analkaline reaction and the mixture has changed from a dark reddish-brownsolution to a yellowish emulsion. To this emulsion is added anadditional 5 per cent by weight of the original acid oil, ofmonoethanolamine, thus making a total of 10 per cent monoethanolamine byweight based on the original weight of acid oil. During the addition ofthe ethanolamine the temperature of the oil rises from 22 C. to 40C. Thefinal mixture is heated with occasional stirring to 100 C. At about 85C. the emulsion is broken and stratification takes place rapidly. Themixture is then allowed to cool to atmospheric temperature in a settingvessel. The lower layer, consisting of monoethanolamine salts of theoil-soluble sulfonic acids dissolved in excess monoethanolamine, isdrawn off from the bottom of the settling vessel.

The alkylolamine layer is subjected to vacuum distillation to separate,the excess monoethanolamine and to recover valuable monoethanolaminesalts of the sulfonic acids. The oil layer is substantially completelyfree of sulfonic acid salts and contains only a very small amount ofmonoethanolamine.

Example 2 In this example, an acid oil similar to that of Example 1 istreated substantially as described above. The removal of the oil-solublesulfonic acids from the acid oil is substantially quantitative. This isapparent from sulfur analyses of the original, sulfonated and finishedoils as follows:

Clay treatment of the finished oil to quantitatively adsorb and removeany remaining sulfonates from the oil gives a treated oil which hassubstantially the same sulfur content as the finished oil before claytreatment. This indicates that substantially all of the sulfonates areremoved from the oil layer by the alkylolamine treatment, and that noadditional washing or similar treatment is necessary to produce afinished oil.

Example 3 An acid oil containing 0.88 per cent sulfur by weight istreated substantially as described in Example 1, with the exception thatthe final mixture of oil and excess monoethanolamine, which is heated toC., is separated into 011 and ethanolamine layers by settling at 100 C.Upon cooling the separated oil layer to atmospheric temperature, a smallamount of ethanolamine separates from the oil but the sulfur contentofthe oil is substantially unchanged, showing that the oil is free ofsulfonic acids.

When accomplishing the separation at elevated temperatures as describedin Example 3, the alkylolamine may be recovered from the oil layer byvacuum distillation without the necessity of additional heating. Thus,the oil layer, at the temperature of separation, may be passed through avacuum flash tower for removal of the alkylolamine. i

The alkylolamine used in the foregoing examples was monoethanolaminebecause this is an eiiective agent in the process and is readilyavailable. Similar results are obtained by substituting for themonoethanolamine an amount of another alkylolamine of the class hereindescribed, especially one of those specifically mentioned,stoichiometrically equivalent to the amount of monoethanolamine employedto neutralize the sulfonic acids and an excess amount equal to theexcess amount of monoethanolamine by volume employed to effect rapidlayer separation.

The process of the invention has been illustrated as a batch extractionprocedure for the sake of simplicity. However, it is also readilyperformed in more complex cocurrent and countercurrent continuousextraction systems with the additional benefits of the inherentadvantages of these systems.

Obviously many modifications and variationsof the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

We claim:

1. In the method wherein a hydrocarbon oil is sulfonated with asulfonating agent, the acid oil layer is separated from the sulfonatingagent layer, and the acid oil layer is neutralized with a base, theimprovement which comprises neutralizing the acid oil layer with analkylolamine incompletely miscible with the neutralized oil and having adensity greater than the density of the neutralized oil, and employing asumcient excess of alkylolamine to dissolve the resulting alkylolaminesulfonic acid salts and form a liquid alkylolamine layer, and separatingthe layers containing in solution substantially all of the alkylolaminesulfonic acid salts formed in the neutralization.

2. In the method wherein a hydrocarbon'oil is sulfonated with asulfonating agent, the acid oil layer is separated from the sulfonatingagent layer, and the acid oil layer is neutralized with a base, theimprovement which comprises neutralizing the acid oil layer with analkylolamine 7, incompletely miscible with the -neutraliaedoilandhavingadensitygreaterthanthedensityot the neutralized oil, andemploying an amount equal to at least per cent oi excess 'alkylolarnineby volume, based on the acid oil, and suflicient to dissolvesubstantially all oi the resulting alkyl-- olamine sulionic acid salts.and form a liquid alkylolamine layerbelow the oil layer. and se aratingthe layers.

8. The method of claim 2, wherein the alkylolamine is soluble in theneutralized oil to the extent oi less than 2 per cent by volume.

- 4. The method of-claim 2, wherein the alkylolamine ismonoethanolamine.

5. In the method wherein a hydrocarbon oil is suli'onated with asuli'onating agent, the acid oil layer is separated irom the sulionatingagent layer, and the acid oil layer is neutralized with a base, theimprovement which comprises neutralizing the acid oil layer withmonoethanolamine, and employing a suiiicient excess of monoethanolamineto dissolve the resulting monoethanolamine sulfonic acid salts and forman oil layer and a monoethanolamine layer, and separating the layerscontaining in solution substantially all of the monoethanolaminesuli'onic acid salts formed in the neutralization.

8. In the method wherein a hydrocarbon oil is sulfonated with asulionating agent, the acid oil layer is separated from the sulionatingagent guano 8". layer. and the acid 011 layer is neutrallaed with abase, the improvement which comprises neutralizing the acid oil layerwith monoethanolamine, employing a suiiicient excess 0! monoethalonamineto dissolve the resulting monoethanolamine sulionic acid salts and formaliquid monoethanolamine layer containing in solution substantially allof the monoethanolamina sulionic acid salts formed in the neutralintm.maintaining the resulting mixture at an elevated temperature at whichrapid stratification oi oil and monoethanolamine layers is accomplished.and separating the layers at said elevated temperature.

'I. The method of claim 6 wherein said elevated temperature is in therange of about 80 to C.

GEORGE RIE'IHOF.

CHAR-LES W. MONTGOMERY. GEORGE P. BROWN, Jl.

REFERENCES CITED The following references are of record in the tile 01'this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,519,930August 22, 1950 GEORGE RIETHOF ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Column 6, lines 67 to 69, inclusive, after the Word layers strike outcontaining in solution substantially all of the alkylolamine sulfonicacid salts formed in the neutralization and insert the same after layerand before the comma in line 66, same column; column 7, lines 25 to 27,inclusive, after layers strike out "containing in solution substantiallyall of the monoethanolamine sulfonic acid salts formed in theneutralization, and insert the same after layer and before the comma inline 24, same column;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case 1n the PatentOffice.

Signed and sealed this 7th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents.

1. IN THE METHOD WHEREIN A HYDROCARBON OIL IS SULFONATED WITH ASULFONATING AGENT, THE ACID OIL LAYER IS SEPARATED FROM THE SULFONATINGAGENT LAYER, AND THE ACID OIL LAYER IS NEUTRALIZED WITH A BASE, THEIMPROVEMENT WHICH COMPRISES NEUTRALIZING THE ACID OIL LAYER WITH ANALKYLOLAMINE INCOMPLETELY MISCIBLE WITH THE NEUTRALIZED OIL AND HAVING ADENSITY GREATER THAN THE DENSITY OF THE NEUTRALIZED OIL, AND EMPLOYING ASUFFICIENT EXCESS OF ALKYLOLAMINE TO DISSOLVE THE RESULTING ALKYLOLAMINESULFONIC ACID SALTS AND FORM A LIQUID ALKYLOLAMINE LAYER, AND SEPARATINGTHE LAYERS CONTAINING IN SOLUTION SUBSTANTIALLY ALL OF THE ALKYLOLAMINESULFONIC ACID SALTS FORMED IN THE NEUTRALIZATION.